Microfluidic devices are becoming increasingly more important in both research and commercial applications. Microfluidic devices, for example, are able to mix and react reagents in small quantities, thereby minimizing reagent costs. These same microfluidic devices also have a relatively small size or “footprint,” thereby saving on laboratory space. For example, microfluidic devices are increasingly being used in clinical applications. Finally, because of their small scale, microfluidic devices are able to quickly and cost effectively synthesize products which can later be used in research and/or commercial applications.
In one type of microfluidic device, various microfluidic features such as channels, chambers, reservoirs, and the like are formed in a disk-shaped device. The disk may include, for instance, a Compact Disk (CD) having microfluidic features formed therein. This disk is then rotated about an axis or rotation (typically the center of the disk) to effectuate movement of fluid from one location to another. Rotation of the disk generally causes the flow of fluid to move toward the edges of the device. There is a need in these types of devices to regulate or modulate the flow of fluid from one location to another. In prior designs, there was no means to stop or otherwise affect fluid transfer once it had been initiated. This poses several problems including the possibility of cross-contamination when fluids from one reservoir or chamber backflow into other chambers or reservoirs. This is significant because as disk-based devices start to incorporate multiple processes like cell lysis, washing, and purification on a single disk, the chance of cross-contamination increases. In addition, in prior designs there is the possibility of fluids leaking out of vent holes located within the disk structure.
For example, in U.S. Pat. No. 6,319,469, each reaction chamber is vented to an air displacement channel located over each reaction chamber. If this venting strategy is used in a configuration where a first chamber is connected to an output chamber located radially outward of the first chamber, fluid transfer occurs from the first chamber to the output chamber. However, assuming a slower flow rate out of the output chamber (e.g., because of the presence of downstream valve, filter, channel restriction and/or microbeads), fluid accumulates in the output chamber and if the output chamber vent is located below the level of the liquid in the first chamber, liquid will leak out of this vent. In another possible configuration, where two chambers are independently connected to an output chamber, if the vent of the output chamber is located above the level of the two input chambers, there is a possibility of backflow into the upstream-located input chambers.
There thus is a need for a device and method that is capable of regulating fluid flow between the various features and elements contained in disk-based microfluidic devices. Such a device should permit the regulation of flow between various chambers or elements without the use of cumbersome and expensive mechanical or electrical valves. In particular, there is a need for a disk design that incorporates the ability to prevent cross-contamination between different chambers that have one or more common channels or outlets.